Long-term blood access required for applications requiring repeated vascular access such as hemodialysis, ultrafiltration, and drug delivery, e.g. chemotherapy, can be problematic due to infection, stenosis, vessel patency, thrombogenesis, and patient compliance. Complications associated with vascular access procedures account for over 20% of hospitalizations of dialysis patients in the United States and cost about $1 billion annually. Although arteriovenous (AV) fistulas have been used for many years in dialysis and other forms of treatment, this procedure can have unfavorable outcomes, particularly in older patients, females, diabetics, and those having co-morbidities such as atherosclerotic vascular disease. Moreover, a maturation period is required subsequent to fistula surgery that may not be feasible in cases of rapid onset of disease. These considerations have led to increased utilization of AV grafts and decreased use of AV fistulas. However, AV grafts are prone to thrombosis usually arising from progressive stenosis at the draining vein, and increased incidence of infection. With regard to dialysis, the Dialysis Outcome Quality Initiative (DOQI) vascular access guidelines published by the National Kidney Foundation advocated the increased prevalence of fistula use among dialysis patients. These guidelines recommend attempting fistula placement in at least 50% of patients, with AV grafts being reserved for patients whose vascular anatomy does not permit construction of a native AV fistula. DOQI guidelines predict that such a strategy will result in 40% of prevalent patients dialyzing with a fistula.
However, deliberately placing AV fistulas in the majority of patients undergoing dialysis or other treatments requiring vascular access increases the frequency of failure due to the marginal nature of vessels within such patients. Moreover, treatment is generally inefficient using AV fistulas and grafts because the blood is withdrawn from and returned to the body using a single AV fistula or graft, particularly where a dual lumen needle is used instead of two needles, which are separated in placement in the fistula. Where there is dual use of the same access site, it is likely that treated and untreated blood will commingle resulting in recirculation or admixture of both treated and untreated blood. In addition, frequent use of needles in either a two-needle or single-needle dual lumen configuration can cause damage to the walls of the vessel rendering the access site unsuitable for treatment.
Implantable vascular access ports can be used to directly contact a vessel and typically consist of an arterial port and a venous port. The ports can improve the efficiency of hemodialysis by reducing admixture and recirculation by being placed on separate vessels. Damage to the wall of the vessels is also reduced because the needles are inserted only into the artificial port, rather than into the vessels themselves. For example, the arterial port can contact an artery using an arterial graft, and the venous port can contact a vein using a venous graft wherein a needle may be inserted into the arterial port for blood “draw” and another needle may be inserted into the venous port for blood “return” to connect the implantable device to the dialysis machine. Alternatively, an AV fistula is created where the blood “draw” is placed on the arterial side of the fistula and the “return” is placed on the venous side of the fistula. Oftentimes, access ports must be placed in close proximity to each other and can result in admixture and recirculation if the same vessel is used. In some cases, an anti-compression structure is used to prevent squeezing of the vessel during insertion of the needle but can be difficult to surgically implant due to the need for special screws and separate parts that must be joined. Specially adapted needles may be used to allow a healthcare practitioner to insert the needle to an appropriate and safe depth every time but operator error is still a problem resulting in suboptimal fluid flow and additional vessel trauma. Additionally, the design of the ports and needles precludes operation by a patient in the absence of technician supervision. Moreover, known access ports tend to slide or rotate on the vessel causing failure of the device particularly during insertion of the needle. During operation, the needle may be unintentionally dislodged by the operator. Although specially adapted needles may be used to allow an operator to insert the needle to an appropriate and safe depth, known access ports lack an optimal means for inserting the needle into the port at a pre-determined length and position. Further, known vascular access devices are not conducive to operation by the patient in which they are implanted due to the complexity of insertion instruments associated with known ports. Known vascular access devices also cause complications such as bleeding and infection, and can result in blood clotting and biocompatibility problems. Notably, interactions between blood components and the materials found within blood processing systems induce the activation of several biological systems such as platelets, complement, and coagulation cascades. Thrombin, an enzyme generated during coagulation, causes blood clotting within blood processing systems, reducing system efficiency. Conventional blood processing systems typically employ the use of anticoagulant drugs, such as heparin, to prevent the formation of blood clots. But prolonged use of anticoagulant drugs without control presents a significant risk of uncontrolled bleeding in patients. Further, known ports do not provide for simplified use or operation such that a patient can administer therapy at home that avoids separate injections of heparin or oversight by a skilled technician or hospital staff for safe and proper usage of the port.
Hence, there is a need for a new improved implantable access port that is an alternative to known vascular access devices and procedures used in ultrafiltration, drug delivery, and kidney dialysis procedures. There is a need for ports having increased patient comfort that reduces the risk of damage to the vessel and frequency of complications. The ports should be easy to use and improve the facility of conducting treatment by medical personnel. There is a need for a simple port that can be easily implanted. The ports should also be easily operated by either a technician or the patient in both clinical and home-use environments. The port must minimize admixture and recirculation. In addition, the port should be able to inhibit infection and thrombogenesis. Further, there is a need for a port that can be reliably affixed onto the vessel subsequent to implantation. The port should prevent squeezing of the vessel during insertion of a needle, cannula or trocar and should be specially configured so that an operator can insert the needle to an appropriate and safe depth every time. There is a need for the safe interchange of untreated and treated blood of a patient through an implanted vascular access port for dialysis or ultrafiltration that will result in increased patient comfort, ease of use by an operator, and will be suitable for longer use than known devices and techniques.